The speaker is ending a relationship they believe is wrong for them, yet cannot stop grieving it. At first they try to talk themselves out of their feelings by dwelling on the other person's flaws. The poem admits this trick doesn't work: the tears come anyway, and at night the speaker dreams of the person and the good memories flood back.
What stands out is the tug-of-war between head and heart. The refrain-like phrase "best for me" appears at the start and again in the final line, but by the end it sounds less like comfort and more like a reminder the speaker is forcing on themselves. The marathon image captures how the person keeps running through their mind without tiring, while the speaker just wants the race to stop.
The closing picture, holding a hand and squeezing it tightly, is the most tender moment. The mood is sad, raw, and honest, with no neat resolution. The title's "ambivalence" fits: letting go is a decision made, but not yet a feeling accepted.